Final answer:
In prophase, the nuclear envelope breaks down and chromatin condenses into visible chromosomes, preparing the cell for division.
Step-by-step explanation:
During prophase, two significant events occur that aid in cell division. Firstly, the nuclear envelope begins to disintegrate into small vesicles, allowing access to the chromosomes. Secondly, the condensation of chromatin into visible sister chromatids happens, which are then moved to opposite poles of the cell by the mitotic spindle being formed by microtubules.
The disassembly of the nuclear envelope ensures that the genetic material is no longer confined to the nucleus, preparing the cell for the subsequent phases of mitosis where the chromosomes will be aligned and separated. The condensation of chromatin is a crucial step because it organizes the DNA into structures that can be easily and equitably divided between daughter cells. It is during this phase that the characteristic X-shaped chromosomes become visible, signifying that the cell is ready to progress through the stages of mitosis.